High pressure fuel carburetor



Jan. 15, 1946. T A; 5T CLMR v 2,393,125

' HIGH PRESSURE FUEL CARBURETOR vAcuuM r. -VALVE MANUAL ENRICHING DEVICEso 23 33 mm 24 FUELINLET 1' 40A l2 P11, 4 l4 EXHAUST MANIFOLD INTAKEMANIFOLD INVENTOR T. STCLAI Q BY V ATTORNEY 1946- T. A. sT CLAIR HIGHPRESSURE FUEL CARBURETOR Filed N ov. 22}. 1941 2 Sheets-Sheet 2 AIRINLET FUEL mu;

INTAKE MANIFOLD INVENTOR T. A. ST CLAIR BY ;7/ M

A ORNE Patented Jan. 15, 1946 PATENT- OFFICE HIGH PRESSURE CARBURETORTheodore A. st. Clair, Pontiac,.Mich., assignor to Phillips PetroleumCompany, a corporation of Delaware Application November 22, 1941, SerialNo. 420.115

\ I 3 Claims.

This invention relates to charge forming deces for internal combustionengines of the type adapted to handle fuels having a considerably highervapor pressure than ordinary gasoline.

Prior to a comparatively recent period, carbureting arrangements forinternal combustion engines were either adapted to handle fuel in anentirely liquid or gaseous state. The ordinary carburetor utilized inthe present day automobile is designed entirely for the carburetion ofliquid fuel. A further type of carburetor was developed inwhich the fuelwas stored in a high pressure tank in liquid phase under pressure and onrelease of pressure the fuel was entirely converted to the gaseous phaseand the arrangement provided means for mixing the gas in the properproportion with air prior to introduction into the manifold. Quiterecently devices have been proposed for the carburetion of fuelmaintained in the liquid phase under pressure in high pressure storagetanks but which assume a liquid and a gaseous phase upon reduction toatmospheric pressure. Quite a number of devices have been suggested forthe separation of fuels of the latter type into two phases andseparately feeding the phases in the proper proportions to the gasolineengine. Some of these arrangements have been successful to some extent,but from a practical standpoint involve rather elaborate and costlyapparatus. The ideal condition for the carburetion of high pressurefuels is one inof vapor lock in carburetors by the use of a heatexchanger located in the conduit for handling liquid fuel to theconventional carburetor inlet,

the heat exchanger having separate passages in heat exchange relationfor the incoming liquid fuel and the vapor fuel after vaporization andmixture with the air stream at the carburetor Jet. This arrangement,although probably satisfactory for use with hydrocarbon fuels having adoes not provide means for accomodating the wide pressurechange whichthese fuels undergo with change in atmospheric conditions. The presentinvention facilitates the carburetion of high pressure fuels in liquidphase and at relatively low pressure by cooling the fuel to asufliciently low temperature that vaporization does not occur onpressure reduction.

An object of the present invention is to provide a liquid feedarrangement for the carburetion of fuels having a considerably highervapor pressure than ordinary gasoline. A further ob- .iect 0f thepresent invention is the. maintenance of the fuel in liquid phase untildischarged from the carburetor jet. Another object is'the' submission ofan arrangement which, with minor adjustments. is capable of convertingthe con-w ventionalinternal combustion engines to the use of ,higherthan normal vapor pressure fuel of high octane number and efliciency. Astill further' object is the deliverance of the high pressure fuel tothe carburetor float chamber at a constant pressure irrespective ofatmospheric conditions, which will enable the conventional .float valveto fishutoif. Another and most. important object is the provision of anarrangement for reducing the pressure of fuels having a considerablyhigher vapor pressure than ordinary gasoline at asufliciently lowtemperature to deliver said fuels to the carburetor jet withoutsubstantialvaporization or the occurrence of vapor lock.

Referringtothe drawings,

Figure 1 illustrates diagrammatically in partial section a preferredform of the present invention.

Figure 2 shows a specially constructed carlouretor embodying'theprinciple of this invention and provided with means for cooling thefloat chamber.

Referring to Figure 1 of the drawings, the numeral l designatesgenerally a standard type of liquid carburetor such as manufactured bythe Carter Company connected with the manifold 2 of an internalcombustion engin through an intake tube extension 3. The mainthrottlevalve t is mounted on a shaft 5 .in' a separate connection 6' andactuated by the foot accelerator (not shown) through the lever B and rod8 in av conventional manner. The throttle in carburetor i has beenremoved. The connection 6 is insulated from the extension 3 by a flange0r gasket 9 of cork, asbestos, or similar material to prevent transferof heat by conduction from said connection'. By positioning the throttlvalve connection on the down-stream side of the heat 55 exchange zonewhere it is subjected to heat radiation from the exhaust manifold, theformation of ice at this point is prevented.

An idling line I connects the carburetor float chamber with the fuelintake tube at the connection 6 and is provided with air and liquidadjustment screws II and I2, respectively. The normal idling jet incarburetor I has been made ineffective. As will be obvious, the idlingfuel from line l0 discharges through orifice |0A into the connection 6at a point just below the edge of the upper half of the butterfly 4 whenclosed. A rod 3 controls the carburetor accelerating pump and mainorifice needle, not shown, from a lever It fixed on the projecting endof the throttle shaft 5. The carburetor is provided with a float chamber|5 having a float l6 actuating a needle valve I! to control the fuelinlet passage |8 according to the liquid level therein. An air inlet l9and choke lever 20 are likewise provided, above the point at which thefuel is introduced into the fuel intake tube from the conventionalcarburetor jet 20A.

The liquid fuel inlet tube 2| is connected to a. high pressure fuelstorage tank,- not shown, which may contain any higher than normal vaporpressure fuel such as 26 or 48 pound Reid vapor pressure naturalgasoline, mixtures thereof or the like. Incidentally, the device of thepresent invention is so constructed and arranged as to handle lowpressure fuels with equal expediency, although it is primarily adaptedfor fuels having a vapor pressure considerably above ordinary gasoline.

The tube 2| prior to connection with the carburetor inlet I8 is coiledaround the fuel intake extension 3, as shown in the drawings. A pressurereducing regulator 22 is connected to the coiled tube, preferably at anintermediate point thereof, adapted to reduce the pressure of the highpressure fuel to a substantially constant value after it has been cooledto a sufficiently low tempera- .diaphragm loader, the core valve isopened wider than during normal regulator operation, venting the vaporthrough the regulator and carburetor and allowing passage of liquid. Thecarburetor then is rapidly cooled. In order to facilitate heat transferfrom the liquid fuel to the vaporous fuel in the intake tube, solder orother suitable conducting material is supplied between thecoils of theliquid tube and between the liquid tubeand the fuel intake tube. Forillustration; the metallic conducting material is shown as extendingonly partially around the extension exposing the inlet tube.

.A vacuum operated shut-off valve 36 is provided in the liquid fuelinlet line just before the fuel enters the carburetor float chamber.This device includes a connection 31 to the starter pedal and a vacuumline 38 communicating with the intake manifold. Depression of thestarter retracts the valve allowing fuel flow into the float chamber andwhen the motor starts, suction from the intake manifold maintains thevalve in open positure. The regulator 22 includes a diaphragm 23 ofsynthetic rubber or other hydrocarbon resistant material clamped betweenthe cap 24 and base 25. The base is secured to the carburetor intaketube and the lower section of the coiled tube 2| is connected to thechamber 26 to the left of the diaphragm by a short tube 21, whichextends directly through the intake tube and hence is subjected to thelow temperature vapors passing to the manifold. A valve core 28, whichmay be of the ordinary tire valve type, is threaded to the interior ofthe tube 21 and the valve stem 29 is provided with an actuating member30 bearing on the bottom of diaphragm 23. The upper section of thecoiled tube 2| connects the outlet of diaphragm chamber 26 with thecarburetor float chamber inlet.

A coil spring 3|, contained within two interfltting and relativelymovable cup shaped members 32 and 33, is interposed between the cap 24'and diaphragm 23, the cup shaped members forming a manually controlleddiaphragm loader. Member 32 is secured to the diaphragm and movabletherewith, while member 33 has an actuating pin 34 which passes throughan opening in the top of the cap. An operating lever 35 is connectedto aBowden cable 35a which extends to the dash-board of the automobile. Bymeans of the foregoing arrangement, engine starving is prevented wherethe motor is stopped for a short period and heat is picked up from theexhaust manifold which may cause some vaporization to take place at theregulator. Bydepressing the regulator valve several times with themanual tion. Since the vacuum operated valve forms no part of thisinvention it will not be described in detail. Other valves, for instanceelectrically operated shut-off valves, may be employed.

In operation, by depressing the starter the shut-off valve 36 is openedwide permitting fuel flow from the cooling coil to the carburetor floatchamber. If the engine has been at standstill,

the small volume of fuel remaining in the float chamber has been heatedand possibly a small amount of evaporation of the lightest ends of thehydrocarbon fuel will take place. The fuel remaining in the floatchamber, however, is supplemented on starting by fresh fuel admittedthrough the shut-off valve and having been deprived of the lighest ends,does not cause vapor lock in the carburetor jets. The fuel passing fromthe high pressure tank, where it is stored under its own vapor pressure,for example, in. the case of 26 pound Reid vapor pressurenatural'gasoline may have a pressure considerably above or below 26pounds per square inch, depending upon atmospheric temperature and thetemperature of the tank. When the engine is started, flow takes placethrough the liquid inlet tube and lower sec tion of the coolingcoil'into the pressure regulator 22. In the pressure regulator 22 thefuel pressure is reduced to from 1.5 to 2.5 pounds per square inch. Theregulator outlet pressure is rather critical inasmuch as pressures muchabove the upper limit will not allow the carburetor float valve to shutoff, while if the pressure falls below the lower limit sufficient fuelis not supplied to the engine upon acceleration.

As the fuel is vaporized in the carburetor let the latent heat ofevaporation necessary to vaporize the fuel is abstracted from theincoming air thereby cooling the vaporto a very low temperature. As thevapor passes downwardly through'the intake tube 3, heat t'ransfertakesplace from the liquid fuel flowing through the liquid fuel inlet tubecoil 2| through the wall ,of the vapor intake tube. The transfer of heatin this manner lowers the temperature of the high pressure fuelsufficiently to enable the reduction of pressure in the pressureregulator without evaporation. The pressure regulator is advantageouslylocated at an intermediate point in the cooling coil to discouragevaporization at the throttling orifice. Ordinarily the temperature isreduced to a suflicient value prior to entry in the regulator to preventvaporization. In extremely warm climates, however, it may be adof theliquid fuel flowing thereto. Referring to Figure 2, wherein aeoaracvantageous to provide a further cooling section. Should the presure'ofthe fuel be reduced without previously being cooled, the light endscontained in the fuel which may constitute which as .50

per cent in liquid volume thereof, are flashed off causing vapor lockand disturbing the fuel metering devices. with the arrangement of thepresent invention, however, pressure reduction to as low a point as from1.5 to 2.5 pounds per square inch can be accomplished withoutsubstantial vaporization either in the cooling 'coil or in thecarburetor float chamber. The pressure is preferably maintained constantwithin this approximate range. After the engine has been started thefuel in the carburetor float chamber is cooled suffloiently so that novaporization occurs in the carburetor jet. The cooling effect of thecold vapors passing to the inlet manifold is adequate to maintainhydrocarbonfuels havingvapor pres sure as high even as 40 pound Reidvapor pres sure natural gasoline in liquid phase. The carburetion ofhigh pressure, high octane fuels is thus possible by the practice of thepresent invention with the conventional carbureting arrangement. Thelabor and expense necessary to make this conversion is very small. Thecarburetor may still be suitable for handling ordinary gasoline withminor adjustments.

The manual diaphragm loader 3t enables rapid starting of the engine inwarm weather when some vaporization may occur in the upper section ofthe cooling coil after the engine has been at standstill for a shortperiod of time and heat transfer has taken place from the exhaustmanifold. Depression of the diaphragm loader through the dashboardcontrol-vents any vapor which may have formed through the regulator andcarburetor which is followed by liquid fuel, rapidly cooling the coiland carburetor float chamber. To avoid icing in and around the mainthrottle valve which tends to occur with the higher pressure fuels, suchas at) pound natural gasoline, the short tubing section 6 which carriesthe throttle valve is placed between the intake tube extension and theintake manifold where The diaphragm chamber ti communicates with thefloat chamber of the carburetor through a passage 52, provided witha-valve t3 likewise of the tire core type. The float chamber at isprovided with a float 5d which closely fits the interior ofthe chamberand actuates the valve 53 through a push pin 85. The float chambercommunicates with the interior of the fuel intake tube through a balanceline 55. By these means the pressure on the fuel in thefioat chamber ismaintained the same as thepressure within the intake tube. The forcetransmitted on the push pin 56 by the float is regulated by means of acoil spring fil contained within a central assage 58 of a cover as. Thecompression of. the spring is regulated by means of an adjustment screw50. The liquid fuel from the float chamber passes to the fuel intaketube through a discharge orifice or jett ti. A needle valve 82 providedwith a lock nut 53 meters the flow of liquid fuel to the discharge jetfrom the float chamber. The fuel intake tube is provided with theconventional venturi t t and main throttle valve 65, as shown in thedrawings.

A shut-off valve, shown diagrammatically at 66, may be connected with avacuum control device as shown in Figure l or a suitable electriccircult. This device is adapted to remain closed during standstill butis opened wide allowing fuel flow to the float chamber when the motor isstarted. 1

The operation of the Figure 2 carburetor is quite similar to that of,the arrangement prevh ously described in connection with Figure 1. Dueto the fact that the liquid inlet tube is coiled around the floatchamber as well as the fuel intake tube to the manifold; heat istransferred from the interior of the carburetor float chamber .to theliquid fuel passing through the coil which in turn loses heat to thecold vap'ors following vaporization at the carburetor jet. With the arrangementof the Figure 2 carburetor the regulator outlet pressure ispreferably set around 2 pounds per square inch. This pressure, however,

it is subjected to heat radiation from the exhaust v manifold 2A.Various other supplemental heating means may be employed for thethrottle such as electrical means or a short section of pipe connectedwith the exhaust manifold and wrapped around the intake tube in thevicinity of the throttle valve.

A modified form of carburetor is shown in Fig ure 2 wherein the fuelline from the high pressure fuel storage tank embraces the carburetorfloat chamber as well as the vapor intake tube to the manifold. Thisarrangement allows the transfer of the cooling effect in the vaporintake tube to the float chamber through the medium for the sake ofbrevity reference numerals'to similar elements in Figure 1 are omitted,the fuel inlet line. 39 from the high pressurefuel storage tank isconnected with a coil tube 40 which surrounds the fuel intake tube M andcarburetor float chamber 62. The cooling coil 40 is connected with apassage 63 which communicates with the pressure regulator, showngenerally at 44, through a the core valve 55. The pressure regulatorincludes a cap at and diaphragm clamped between the cap and the body of.the'carburetor. A valve operating element or push pin" is held betweenthe valvestem 49 and. the diaphragm 41' by a loading spring and thevalve spring, not shown.

the core valve is balanced by the adjustable spring 51 which acts as aloading'means for the float.

It is thus obvious that by the arrangement of the presentinvention-fuels having a considerably higher pressure than ordinarygasoline may be employed with expediency, thereby utilizing hydrocarbonfractions hitherto considered im-= practical as a fuel for internalcombustion engines. The degree of cooling necessary to maintain the fuelin liquid phase following pressure reduction varies as to. theparticular fuel being employed. In the case of 26 pound natural gasolinea temperature reduction to approximately 60 F. is suflicient, while asomewhat lower temperature, 1. 'e., about 416 F. is necessary in thecase of 401 pound natural gasoline. The cooling coil, of course, is ofsuillcient length to secure the desired results and may be provided witha valved bypass prior to the point of pressure reduction to regulate'thedegree of cooling for the specific fuel employed. This and other changesandmodifications may be made in the arrangement shown in theaccompanying figures without departing from the spirit and scope of thepresent invention.

therein, an engine mixture inlet tube for leading the vapors from saidcarburetor to the intake manifold of the engine, a liquid fuel inlet forincoming high pressure fuel, conduit means surrounding the enginemixture inlet tube for conveying said incoming fuel from said inlet tosaid carburetor, the liquid fuel being cooled as it is conveyed to saidcarburetor by the heat exchange relationship between the conduit meanssurrounding the engine mixture inlet tube and the vaporized fuel in theengine mixture inlet tube to thereby prevent vaporization of said liquidfuel at least until it reaches the main jet in the carconduit means atan intermediate point therein 7 comprising a reducing valve, said valvebeing loaded by a spring pressed diaphragm and provided with manuallyoperated means for opening said valve wider than normal in starting theenglue and said reducing valve being coo ed by heat exchange relationwith the engine mixture inlet tube for reducing without vaporizing thepressure buretor, pressure reducing means located in the conduit meansat an intermediate point therein and said'pressure reducing means beingcooled by heat exchange relation with the engine mixture inlet tube forreducing without vaporization the pressure of said liquid fuel before itreaches said float-operated valve to a constant low value for therebypreventing interference with free operation of said valve.

1 2. A device used for carbureting a high pressure liquid fuel andfeeding the same to an internal combustion engine comprising, incombination, a carburetor having a main liquid fuel jet, a float chamberand a float-operated valve of said liquid fuel before it reaches saidfloatoperated valve to a constant low value, for

thereby preventing interference with free operation of said valve.

3. A device used for carbureting a high pressure liquid fuel and feedingthe same to an internal combustion engine comprising, in combination, acarburetor having a main liquid fuel jet, a float chamber and afloat-operated valve therein, an engine mixture inlet tube for leadingthe vapors from said carburetor to the intake manifold of the engine, aliquid fuel inlet for incoming high pressure fuel comprising a tubecoiled about said engine mixture inlet tube from the engine side to thecarburetor side thereof,

I the liquid fuel being cooled as it is conveyed to therein, an enginemixture inlet tube for leading the vapors from said carburetor totheintake manifold of the engine, a liquid fuel inlet for incoming highpressure fuel, conduit means surrounding the engine mixture inlet tubefor conveying said incoming fuel from said inlet to said carburetor, theliquidfuel being cooled as it is conveyed to said carburetor by the heatexchange relationship between the conduit means surrounding the enginemixture inlet tube and the vaporized fuel in the engine mixture inlettube to thereby prevent vaporization of said liquid fuel at least untilit reaches the main jet in the car buretor, pressure reducing meanslocated in the said carburetor by the heat exchange relationship betweenthe conduit means surrounding the engine mixture inlet tube and thevaporized fuel in the engine mixture inlet tube to thereby preventvaporization of said liquid fuel at least until it reaches the main jetin the carburetor, pressure reducing means located in the conduit meansat an intermediate point therein and said pressure a reducing meansbeing cooled by heat exchange relation with the engine mixture inlettube for reducing without vaporization the pressure of said liquid fuelbefore it reaches said float-operated valve to, a constant low value forthereby preventing interference with free operation of said valve.

